Reactor power regulators have been developed for nuclear power plants in which thermal energy of steam generated by a reactor or a steam generator provided independently of the reactor is converted into electrical energy by a turbine and a power generator, the apparatuses being intended to regulate a reactor output (power) in a range from a plant stop state to a rated power generator output at the time of plant activation and stop or in a daily load following operation that deals with electric power load fluctuations during daytime and nighttime. Examples of the conventional reactor power regulators are illustrated in FIGS. 8 and 9.
In the conventional nuclear reactor power regulator as a first configuration example illustrated in FIG. 8, a central load dispatching center 1 or an operator 2 inputs an operation pattern (signal) 101 to an interface device 3. The interface device 3 inputs a reactor output target value (signal) 102 (which will be simply referred to as “target value 102”, hereinafter) and a reactor output change rate (signal) 103 (which will be simply referred to as “change rate 103”, hereinafter) to a reactor output controlling device 4 in accordance with the operation pattern 101. Instead of the operation pattern 101, the central load dispatching center 1 or the operator 2 can also input the target value 102 and the change rate 103 directly to the interface device 3.
The reactor output controlling device 4 calculates a reactor output control signal 108 (which will be simply referred to as “signal 108”, hereinafter) using the target value 102, the change rate 103, and a reactor output equivalent signal 106 (which will be simply referred to as “equivalent signal 106”, hereinafter). The reactor output controlling device 4 calculates the signal 108 according to, for example, the following method. The signal 108 is calculated as a signal for controlling the reactor to a reactor output set value 118 (which will be simply referred to as “set value 118”, hereinafter).
(1) The set value 118 is calculated in accordance with the change rate 103, from a power generator output 106a corresponding to the reactor output equivalent signal 106 at the time of control start. The calculation is performed by a reactor output setting element 41 of the reactor output controlling device 4 until the set value 118 reaches the target value 102.
(2) After the power generator output (signal) 106a and a deviation 118a between the power generator output 106a and the set value 118 calculated by the reactor output setting element 41 are input to a controlling element 42, the controlling element 42 calculates the signal 108. The calculation is performed until a deviation between the set value (signal) 118 and the equivalent signal 106 is eliminated.
A deviation between a pressure controller output signal and the signal 108 may be used to calculate the signal 108, as needed. Here, the pressure control output signal is calculated based on a deviation between a main steam pressure signal and a main steam pressure set value (signal).
A reactor output controller 7 actuates a reactor output controlling equipment 8 by using the signal 108. For example, in a case of a boiling water reactor, a recirculation flow controlling unit included in the reactor output controller 7 outputs a reactor output controlling equipment actuation request signal 109 (which will be simply referred to as “signal 109”, hereinafter) using the signal 108, to thereby change a drive state of a reactor recirculation pump 8a included in the reactor output controlling equipment 8 and thus changes a recirculation flow (flow rate).
A reactor output, a main steam flow (flow rate), and the power generator output 106a change along with the change of the recirculation flow. The signal 108 is continuously output by the reactor output controlling device 4 until the deviation between the power generator output 106a and the set value 118 is eliminated, whereby the reactor output can be regulated to the target value.
Conventionally, in a normal operation, nuclear power plants are operated so that the power generator output is a rated value (100%). The reactor output at the time of the rated power generator output is different depending on cooling water temperature for cooling a condenser of a steam turbine. In seasons in which the cooling water temperature is low, power generation efficiency is high, and hence the reactor output is set to be lower so that the rated power generator output is maintained. Meanwhile, in an operation that tends to be adopted more and more in recent years, a larger amount of electric power is output while the reactor output is maintained at a rated reactor power.
In this case, a value generally adopted as the reactor output is a reactor output signal calculated by a reactor output calculating device. The reactor output calculating device performs computation based on a thermal equilibrium from various necessary plant state quantities for each predetermined period of time. Accordingly, development of nuclear reactor power regulator that uses the following signals as the equivalent signal 106 instead of the power generator output 106a to thereby automatically perform a rated reactor power (output) constant operation has been started as described in Patent Document 1 (see FIG. 9).
That is, in the conventional nuclear reactor power regulator as a second configuration example illustrated in FIG. 9, the conventional nuclear reactor power regulator as the second configuration example uses: (A) a reactor output signal 105 (which will be simply referred to as “signal 105”, hereinafter) calculated by a reactor output calculating device 5 that performs computation based on a thermal equilibrium from various necessary plant state quantities (parameters) 104; (B) a signal 206b obtained by correcting and converting an APRM signal 106b in a neutron instrumentation system of the reactor, using a conversion factor set in consideration of degradation over time of a detector and the like; and (C) a signal 206a obtained by correcting and converting the power generator output 106a using efficiency that depends on a degree of condenser vacuum and the like, as the equivalent signal 106 instead of the power generator output 106a. 
Unfortunately, in a case where control is performed using a power generator output signal and the like in the conventional nuclear reactor power regulator, even if a deviation from the signal 105 occurs, it is difficult to eliminate the deviation. In consideration of above-mentioned circumstance, at present, the nuclear reactor power regulation (adjustment) from a rated power generator output to a rated reactor power and a rated reactor power constant operation are manually performed.